Inhibition and Allosteric Regulation of Monomeric Phosphoenolpyruvate Carboxykinase by 3-Mercaptopicolinic Acid
Inhibition and Allosteric Regulation of Monomeric Phosphoenolpyruvate Carboxykinase by 3-Mercaptopicolinic Acid
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DOI：
10.1021/acs.biochem.5b00822
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发表时间：
2015-09-29
期刊：
影响因子：
2.9
通讯作者：
Holyoak, Todd
中科院分区：
文献类型：
--
作者：
Balan, Marc D.;Mcleod, Matthew J.;Holyoak, Todd
近40年来，人们已经知道色氨酸代谢物和吡啶甲酸类似物作为抑制剂的异生。早期研究发现3-巯基吡啶甲酸（MPA）是一种有效的降血糖剂，其通过特异性抑制葡萄糖生成途径中的磷酸烯醇丙酮酸羧激酶（PEPCK）来抑制葡萄糖合成。尽管以前的动力学研究，MPA的抑制机制尚不清楚。为了阐明MPA对PEPCK的抑制机制，我们进行了结构和动力学研究。与MPA复合的PEPCK的晶体结构和反应底物一致的动力学数据表明，PEPCK被MPA在两个离散结合位点的结合所抑制：一个以竞争方式与PEP/OAA（类似于1.0 μ M）起作用，另一个作用于先前未鉴定的变构位点（Ki类似于150 μ M）。结构研究表明，MPA的结合变构口袋稳定的核苷酸结合位点的构象改变，这反过来又降低了酶的亲和力的核苷酸。
For almost 40 years, it has been known that tryptophan metabolites and picolinic acid analogues act as inhibitors of gluconeogenesis. Early studies observed that 3-mercaptopicolinic acid (MPA) was a potent hypoglycemic agent via inhibition of glucose synthesis through the specific inhibition of phosphoenolpyruvate carboxykinase (PEPCK) in the gluconeogenesis pathway. Despite prior kinetic investigation, the mechanism of the inhibition by MPA is unclear. To clarify the mechanism of inhibition exerted by MPA on PEPCK, we have undertaken structural and kinetic studies. The kinetic data in concert with crystallographic structures of PEPCK in complex with MPA and the substrates for the reaction illustrate that PEPCK is inhibited by the binding of MPA at two discrete binding sites: one acting in a competitive fashion with PEP/OAA (similar to 1.0 mu M) and the other acting at a previously unidentified allosteric site (K-i similar to 150 mu M). The structural studies suggest that binding of MPA to the allosteric pocket stabilizes an altered conformation of the nucleotide-binding site that in turn reduces the affinity of the enzyme for the nucleotide.